Erosion & Transportation

Abrasion: When the load the river is carryig repeatedly hits the river bed causing some of the material to break off.

Attrition: When the stones and boulders carried by the river knock against each other and over time are weakened, causing bits to fall off and reduce in size.

Solution: When the river flows on certain types of rock such as chalk and limestone - they're soluble in rainwater.

Traction: Largest material: too heavy to lose contact with the bed so it's rolled along.

Saltation: Small stones and frains of sand bouncing along the bed. Lighter load.

Suspension: Carrying fine material that floats in the river

Solution: Dissolved load (chalk and limestone)

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Long Profile

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Waterfalls and Gorges

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Meanders and Oxbow Lakes

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Levees and Floodplains

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River Discharge

Precipitation: Any moisture reaching the ground

Interception: Water being prevented from reaching the surface by trees or grass

Surface Storage: Water held on the ground surface

Infiltration: Water sinking into soil/rock from the surface

Soil Moisture: Water held in the soil layer

Percolation: Water seeping deeper below the surface

Groundwater: Water stored in the rock

Transpiration: Water lost through pores in vegetation

Evaporation: Water lost from ground/vegetation

Surface Run-off: Water flowing on top of the ground

Throughflow: Water flowing through the soil layer parallel to the surface

Groundwater Flow: Water flowing through the rock layer

Water Table: Current upper level of saturated rock/soil where no more water can be absorbed

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Storm Hydrograph

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Bangladesh

2004 - July to September

In July

40% of Dhaka was underwater

60% of the country submerged

600 deaths

30 million homeless

100,000 people had diarrhoea

As the year progressed

750 dead

Dhaka airport flooded

$7 billion schools and hospital damage

Rice was washed away

Aftermath:Food supplies, medicines, clothing and blankets distributed. Transport system difficult. Local communities rebuilt their homes. Disease was a threat. UN appealed for $74 million, but had received only 20% by September. WaterAid helped too.

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Hard Engineering

Involves the use of technology in order to try to control rivers.

Multi-purpose Project: The Three Gorges Dam, China

Constructed at Yichang on the River Yangtse

Benefit 15 million people in high-risk flood areas

Protect 25,000 hectares of farmland

Yangtse used to carry over 500 million tonnes of silt every year

50% of it is now deposited behind the dam

1.4 million people were forced to relocate

$30 million of the funds set aside for the project has been taken by corrupt local officials

Straightening Meaneders

In this way the river is made to follow a new shorter, straight section and abandon its natural meandering course.

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Soft Engineering // Water Supply

Floodplain Zoning: where the flood risk across different parts of the floodplain is assessed and resulting land use takes this into account.